Shanghai
Should you be admitting that
. In the 70's and 80's the Russians did not use them in their arctic circle bases so we had better opportunities to penetrate some of the fjords leading up to their bases.    ??

Re the museum. The site is the old HMS Dolphin as in Cyril Tawney's song Diesel And Shale, "The big man at dolphin he sent for me"
Be sure to take the guided tour of the sub. A grizzled old submariner takes you around and has a story to go with each section.
You will see a big tower which is where the submariners have to practice escaping, exhaling all the way up just as in your story Robomatic, or their lungs would indeed burst.

At Portsmouth, take a harbour tour boat. The museum is one of the stops and you can use your ticket to get on another boat later.

There's a smell in the air...
Keith.